It is known that leads used in cardiac stimulation are often implanted transvenously or transthoracically with the result that the lead body can be physically crushed by either bones (i.e. "first rib-clavicle") or by tissue (costoclavicular ligament complex, subclavius muscle) and by anchoring sleeves which are tied-down so tightly that the lead body can be crushed or damaged.
The result of these crushing or constrictive stresses, which are made more pronounced by movements of the patient, can become manifested by severe damage to the conductors, such as by abrasion of the insulation of the conductors within the lead body which, in turn, can result in failed conductors and/or failed insulation. This is because the conductors within the lead are usually disposed in close proximity to one another. For example, in a tripolar pacing lead, at least three conductors would be housed within the lead and must be maintained in a spatially disposed relationship with one another.
Conductor mechanical damage including fractures and/or insulation breaks may occur in about 2% to 3% of implanted leads. In patients who are not pacemaker dependent, a failure event is usually not life-threatening, but can require corrective procedures with potential for complications. Mechanical damage can occur as coil deformation, coil fracture, mechanically induced insulation breaches, and insulation wear observed individually or in combination.